Ignition circuit for lamps

ABSTRACT

An ignition circuit for lamps such as gaseous discharge lamps as, for example, fluorescent lamps, including a series-resonant circuit having a quality factor Q of from 2 to 5. The series resonant circuit is connected to an electronic switch and the lamp is coupled across the series combination of one impedance of the resonant circuit and the electronic switch. The electronic switch exhibits the characteristic of automatically opening or disconnecting after a predetermined time delay. The lamp may therefore be ignited with the shunt impedance of the seriesresonant circuit being disconnected from the lamp after ignition.

United States Patent [191 June 18, 1974 Peltz IGNITION CIRCUIT FOR LAMPS [75] Inventor: Giienter Peltz, Wasser, Germany [73] Assignee: ITT Industries, Inc., New York,

[22] Filed: Sept. 26, 1972 [21] Appl. No.: 292,374

[30] Foreign Application Priority Data Oct. 11, 1971 Germany 2150576 [52] US. Cl 315/244, 315/D1G. 5, 315/205 [51] Int. Cl. 1105b 37/00 [58] Field of Search 315/DIG. 5, 205, 207, 242, 315/243, 244

[56] References Cited UNITED STATES PATENTS 2,046,980 7/1936 Vanwijk 315/243 3,280,369 10/1966 Baum et a1 315/243 3,383,558 5/1968 Waymouth 315/242 3,679,936 7/1972 Moerkins 315/205 Primary Examiner-Herman Karl Saalbach Assistant Examiner-Lawrence J. Dahl Attorney, Agent, or Firm-Menotti J. Lombardi, .lr.; John T. OHalloran; Peter Van Der Sluys 57] ABSTRACT An ignition circuit for lamps such as gaseous discharge lamps as, for example, fluorescent lamps, including a series-resonant circuit having a quality factor Q of from 2 to 5. The series resonant circuit is connected to an electronic switch and the lamp is coupled across the series combination of one impedance of the resonant circuit and the electronic switch. The electronic switch exhibits the characteristic of automatically opening or disconnecting after a predetermined time delay. The lamp may therefore be ignited with the shunt impedance of the series-resonant circuit being disconnected from the lamp after ignition.

9 Claims, 9 Drawing Figures 1 IGNITION CIRCUIT FOR LAMPS BACKGROUND OF THE INVENTION for the lighting of rooms, are known. One prior art circuit uses a series-resonant circuit tuned to the resonant or operating frequency. The operating frequency is substantially higher than the usual power line frequency of 50 or 60 Hertz. The resonance voltage of the resonant circuit (which is higher than in the case of non-tuning), reaches the ignition voltage of the lamp. As is well known, this ignition voltage is substantially higher than the conducting or normal operating voltage of the lamp.

In prior art circuits, the two impedances of the resonant circuit, which are dual in relation to one another, namely a choke and a capacitor, are permanently connected to the incandescent lamp. Investigations have shown, however, that this mode of operation bears certain disadvantages. The invention, therefore, is based on the problem ofimproving the known resonance ignition method for incandescent lamps.

SUMMARY OF THE INVENTION Accordingly it is an object of this invention to provide a resonant ignition circuit for lamps without a control grid.

It is another object of this invention to provide a resonant ignition circuit for lamps with or without filament electrodes.

An ignition circuit for igniting a lamp that is energized by a power source includes a series-resonant circuit including an inductive impedance and a capacitive impedance. An electronic switch is coupled in series with the resonant circuit across the power source and the switch exhibits the characteristic of automatically opening or disconnecting after a predetermined time delay. The series combination of one of the impedances and the electronic switch are shunted across the lamp so as to ignite the lamp and then disconnect the one impedance from the lamp after the predetermined time delay. v

Other objects and features of this invention will become more apparent by reference to the following description taken in conjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic circuit diagram of one embodiment of the invention;

FIGS. 2 through 6 are schematic circuit diagrams of other examples that include diodes in the electronic switch exhibiting automatic disconnect after a predetermined time delay; and

FIGS. 7 through 9 are schematic circuit diagrams of other embodiments of the invention that serve as ignition circuits for the combination of two parallel lamps.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1 there is shown as an embodiment of a circuit arrangement suitable for carrying out the inventive method. In the example shown in FIG. 1, the impedance connected in parallel with the lamp LR, is the capacitor C. The capacitor C is disconnected from the lamp subsequent to the ignition, by the glow starter St. A choke L preceding the lamp in the usual way as a stabilizing element, is connected with its one end to the one filament f of the lamp while the other end of this filament is not connected. In the same way there is connected the second filament of the lamp, i.e., the one end thereof extends to the one pole of the glow starter St and then, via the on-off switch S, to the one pole of the supplying a.c. voltage source U the other pole of which is connected to the choke L. p

The series-resonant circuit constituted by the two impedances L and C is tuned to the frequency of the source of a.c. voltage U and has a quality factor or Q of from 2 to 5, so that accordingly, the ignition voltage as applied to the lamp is substantially higher than the peak voltage of the source of a.c. voltage.

Upon switching on the a.c. voltage U by the switch S there is first of all ignited the glow starter St which then connects the capacitor C in parallel with the lamp LR. The voltage applied to the lamp builds itself up until ignition of the lamp is effected, whereupon the glow starter St again disconnects the resonant circuit impedance C from the lamp. Ignition of the lamp is effected with the aid of this circuit without causing any flickering, but it takes some time, under certain circumstances several seconds, until the lamp is ignited.

FIG. 2 shows an improved resonance ignition circuit which no longer has this disadvantage of the delayed switching on. In FIG. 2, unlike in the arrangement'according to FIG. I, the capacitor C is arranged before the lamp LR while the choke L, via the electronic switch to be explained in greater detail hereinafter, is arranged in parallel with the lamp.

The possibilities shown in FIGS. 1 and 2, of providing the lamp with the two impedances L and C, are equivalent to one another as regards the ignition effect, but the arrangement according to FIG. 2, under certain circumstances, may be more favorable from a cost-saving point of view, because the choke L is only operated temporarily and only needs to be dimensioned for a substantially smaller load.

The electronic switch disconnecting automatically with a time delay, in the example of embodiment shown in FIG. 2, consists of a pair of unidirectional conducting devices such as diodes D1 and D2 which are seriesconnected and poled in the same direction. At the junction or connecting point of the diodes, there is attached one end of the choke L. The resistor R1 and likewise also the capacitor C1 are connected in parallel with the series arrangement of the two diodes D1 and D2. The common connecting point of the cathode of diode D2, the resistor R1 and the capacitor C1 is connected to both the lamp LR and the switch S, but just as well also the connecting point of the anode of diode D1, the resistor R1 and the capacitor C1 could be connected to the lamp LR and the switch S.

For reducing the required dielectric strength of the capacitor C1, the arrangement according to FIG. 2 can be modified in the way shown in FIG. 3, namely instead of the capacitor C1, according to FIG. 2, there are provided two series-connected capacitors C2 and C3, with the common connecting point thereof being attached to both the lamp LR and the switch S. As regards the wiring or equipping with the two impedances L and C, the arrangement according to FIG. 3 corresponds to that of FIG. 1.

At the instant of switching on the source of ac. voltage U B in the arrangements shown in FIGS. 2 and 3, the two diodes D1 and D2 are connected antiparallel across the capacitor C1 or the capacitors C2 and C3 respectively, until the capacitors are charged, so that the diodes D1 and D2 are blocked. Appropriately, the capacitors are so dimensioned that the two diodes are only rendered non-conductive after the lamp has been ignited, and the corresponding time constant can be easily ascertained empirically. Upon disconnection of the source of ac. voltage U the capacitors discharge across the resistor R1, so that the arrangement is ready to be switched on again after a short period of time.

FIG. 4 shows a particularly suitable further embodiment of the arrangements described hereinbefore, by which the capacitance value of the capacitors C1 or C2 and C3 according to FIGS. 2 or 3 respectively, can be substantially reduced. To this end there are used the two transistors TI and T2 provided according to FIG. 4. These transistors are connected in such a way that the capacitors C4 and C5 corresponding to the capacitors C2 and C3 according to FIG. 3, are connected between the base and the collector of the corresponding transistor T1 or T2 respectively. The capacitance of the capacitors C4 and C5 between the collector and the emitter of the respective transistor, appears to be enlarged by the corresponding current gain factor in a grounded emitter arrangement.

The circuit according to FIG. 4 again consists of the two impedances C and L, with the capacitor C being inserted before the lamp LR, and the choke L being connected parallel in relation thereto. The electronic switch automatically disconnecting with a time delay consists of the series arrangement of the two diodes D3 and D4 in the same direction, to the common connecting point of which there is connected the choke L. The resistor R2, the capacitor C4 and the collector of transistor T1 are connected to the cathode of diode D3, whereas the other end of resistor R2, the anode of diode D5, and the emitter of transistor T1 are connected to the filament f of the lamp LR and to the switch 5. The base of transistor T1 is applied to the common connecting point of both the capacitor C4 and the cathode of diode D5.

A network which is of the same kind as regards the employed components, and which consists of the resistor R3, the capacitor C5, the diode D6 and the transistor T2 is assigned to the other diode. The arrangement of these components is made in such a way that the emitter of transistor T2, the anode of diode D6 and the resistor R3 are connected to the anode of diode D4, whereas the collector of transistor T2, the capacitor C5 and the other terminal of resistor R3 are connected to the filament of the lamp and to the switch S. The base of transistor T2 is applied to the common connecting point of both the capacitor C5 and the cathode of diode D6. Instead of the transistors T1 and T2 it is also possible to use other current-amplifying elements; this may be of advantage especially when the current-amplifying elements have a current gain factor higher than the one customary with transistors, because in this way capacitances of capacitors C4 and C5 to be used, can be reduced still further, which will thus result in a saving of space.

Instead of connecting two diodes in series in the same direction as shown in FIGS. 2 to 4, it is also possible for the electronic switch of the type disconnecting automatically with a time delay, to be built up from a diode bridge arrangement with the corresponding capacitors and resistors. This is shown in FIGS. 5 and 6. In the arrangement according to FIG. 5 the bridge consists of the diodes D7, D8, D9 and D10, with the one diagonal thereof, hence the connecting points between the diodes D7 and D8 or D9 and D10, being connected in series with the impedance which is arranged in parallel with the lamp LR. The other diagonal of this bridge, hence the connecting points of the diodes D8 and D10 or D7 and D9, is respectively bridged by the capacitor C6 and the resistor R4, so that this capacitor is capable of charging and discharging in the way as already described hereinbefore.

FIG. 6 includes the arrangement shown in FIG. 5 enlarged by the step according to FIG. 4, i.e., the capacitor C6 according to FIG. 5 has been replaced by the transistor T3, the diode D11 and the capacitor C7. It will be seen that the cathode of diode D11, together with the one plate of the capacitor C7 is connected to the base of transistor T3 while the collector thereof is connected to the diagonal point constituted by the cathodes of the diodes D8 and D10, to which there is also applied the other plate of the capacitor C7, whereas the emitter of the transistor T3, together with the anode of the diode D11 is connected to the diagonal point constituted by the anodes of the diodes D7 and D9. Moreover, there still exists the resistor R5 as connected between the collector and the emitter of transistor T3.

FIGS. 7 to 9 show circuit arrangements with the aid of which the two lamps LR and LR can be ignited simultaneously, as is already known from ignition circuits not operating on the resonance ignition principle; according to the known technology, such circuits are referred to as so-called lead-lag (duo) circuits. The arrangement according to FIG. 7 is made in such a way that the choke L is inserted before, and the capacitor C is connected in parallel with the lamp LR, whereas the capacitor C is inserted before and the choke L is connected in parallel with the lamp LR. As an electronic switch of the type automatically disconnecting with a time delay there is used in this particular case an arrangement resembling those shown in FIG. 3 but which, however, as regards the series arrangement to be used of two diodes in the same direction, is doubled so that there will also result a bridge arrangement resembling that shown in FIG. 5.

The series arrangement of the diodes DI and D2 in the same direction is connected in parallel in the same direction with the series arrangement of the diodes DI and D2 in the same direction, while as regards the wiring with the resistor R1 and the capacitors C2 or C3, the circuit is identical to that shown in FIG. 3. At the connecting point A, consisting of the cathode of diode D1 and the anode of diode D2, there is connected the capacitor C which is arranged in parallel with the lamp LR (LR whereas at the respective connecting point B of the diodes D1 and D2 there is connected the choke L which is arranged in parallel with the lamp). The common connecting point D of the two capacitors C2 and C3 is applied to the two filaments and the switch S.

The arrangement shown in FIG. 7, according to the circuit section shown in FIG. 8, can also be extended to a bridge circuit arrangement according to FIG. 5 for effecting ignition of the two lamps. In such a case, as

may be taken from FIG. 3, the additional series arrangement in the same direction of the diodes D1 and D2 according to FIG. 7 is added to the bridge circuit according to FIG. 5 consisting of the diodes D7, D8, D9 and D10, in such a way that this series arrangement, together with the capacitor C6 and the resistor R4 respectively arranged in parallel therewith, will come to lie in the one bridge diagonal, i.e., in that particular one constituted by the connecting points of the anodes of the diodes D7 and D9 or the cathodes of the diodes D8 10 and D10 respectively.

In the case of FIG. 8, the connecting point A according to FIG. 7 is constituted by the common connecting point of the diodes D1 and D2, and the connecting point B according to FIG. 7 is constituted by the common connecting point of the diodes D7 and D8, while the common connecting point D according to FIG. 7 is constituted by the common connecting point of both the diodes D9 and D10.

Again, the arrangement according to FIG. 8 can be enlarged in such a way that, as regards the wiring of the capacitor C6 or C7, there will result an arrangement corresponding to that of FIG. 6, i.e., there are likewise provided in FIG. 9 the components as provided for according to FIG. 6, namely the diode D11, the capacitor C7, the transistor T3 and the resistor R5.

It should be emphasized and is within the scope of the invention that, although the examples of embodiment according to FIGS. 1 to 9 are all made in such a way that the filaments of the respectively shown lamps are not traversed by a heater current, the various circuit arrangements used for carrying out the inventive method, of course, can be modified in a simple way in order to achieve that incandescent lamps are heated. To this end it is merely necessary for the series arrangement consisting of the impedance arranged in parallel with the incandescent lamp and of the electronic switch automatically disconnecting with a time delay, to be not arranged in parallel with the incandescent lamp in the way as shown in FIGS. 1 to 7, but to connect, via this series arrangement, the two ends of the two filaments to one another which, in the drawings, are shown to be free.

While the principles of the invention have been described in connection with specific structure it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention as set forth in the objects thereof and in the accompanying claims.

What is claimed is:

1. An ignition circuit for igniting a lamp that is energized by a power source comprising in combination:

a series-resonant circuit including an inductive impedance and a capacitive impedance;

an electronic switch, of the type that automatically disconnects after a predetermined time delay, coupled in series with said resonant circuit and said power source, said switch including a resistor, a capacitor coupled in parallel with said resistor, and a pair of series connected diodes both in the same direction and coupled across said resistor, one of said impedances being coupled to the junction of said diodes; and

means for coupling the series connection of said one 6 impedance and said electronic switch across said lamp whereby said lamp is ignited and thereafter said one impedance is disconnected from said lamp by said electronic switch after a predetermined time delay. 2. The combination in accordance with claim 1 that further includes I 5 a second capacitor coupled to said one capacitor with the serial combination of said capacitors being coupled across said resistor.

3. The combination in accordance with claim 1, wherein said one impedance comprises an inductor.

4. The combination in accordance with claim 2, wherein said one impedance comprises a capacitor.

5. An ignition circuit for igniting a lamp that is energized by a power source comprising in combination:

a series-resonant circuit including an inductive impedance and a capacitive impedance;

an electronic switch of the type that disconnects automatically with a time delay and includes:

a bridge connection of four diodes, said bridge having four junctions, a first junction connecting anodes of a first pair of diodes, a second junction connecting cathodes of a second pair of diodes and third and fourth junctions each connecting a cathode of the first pair of diodes to an anode of the second pair of diodes,

a resistor,

a capacitor connected in parallel with said resistor, said parallel connection being connected across the first and second junctions, the third and fourth junctions being connected to the seriesresonant circuit and the power source, so that said switch is in series therewith; and

means for coupling the series connection of one of said impedances and said electronic switch across said lamp whereby the lamp is ignited and thereafter the one impedance is disconnected from said lamp by said electronic switch after a predetermined time delay.

6. The combination in accordance with claim 5, that further includes a further diode connected in series with the capacitor such that the cathode of said diode is connected to said capacitor and the anode thereof to the junction constituted by the anodes of two bridge diodes, and that to the point connecting said capacitor to said further diode there is connected the base of a transistor with the emitter thereof being connected to the anode of said further diode and with the collector thereof being connected to the junction constituted by the cathodes of two bridge diodes.

7. A circuit for the ignition of two lamps in accordance with claim 3, additionally comprising:

a second pair of serially connected diodes both in the same direction and coupled in parallel with and in the same direction as the first pair of diodes;

a second series-resonant circuit including an inductive impedance and a capacitive impedance, said inductive impedance connected to said power source and the capacitive impedance connected to the junction connecting the second pair of series connected diodes; and

means for connecting a second lamp in parallel with the capacitive impedance of the second seriesresonant circuit, the second pair of diodes and the resistor and capacitor of the electronic switch.

8. An ignition circuit for igniting a lamp that is energized by a power source comprising in combination:

3 ,8 1 8 ,268 7 8 a series-resonant circuit including an inductive impetime delay.

dance and a capacitive impedance one of said im- 9. An ignition circuit for igniting a laMp without a pedances connected in parallel with said lamp; control grid for energization from a source of alternata pair of diodes connected in series in the same direcing energy comprising in combination:

tion, with the common connecting point thereof being connected to the impedance connected in parallel with said lamp, whereas on one hand the cathode of the one diode across a resistor and a transistor connected in parallel therewith, is cona series-resonant circuit including a capacitive impedance and an inductive impedance;

an electronic switch serially connected to said resonant circuit and said source of alternating energy, said electronic switch including,

nected in such a way to said lamp, that the collec- 0 a pair of series connected diodes coupled to said tor thereof is connected to the cathode of the one resonant circuit at their junction so that one of diode whose emitter is applied to the lamp and said diodes conducts on one alternation of said whose base, on one hand, via a capacitor is conalternating energy and the other of said diodes nected to the cathode of the one diode and, on the conducts on an opposite alternation of said alterother hand, via a further diode is applied with its nating energy, so that a resonant voltage signal is cathode to the base of the transistor, is connected to the lamp whereas, on the other hand, the anode of the other diode, across a further resistor and a further transistor connected in parallel therewith,

is connected to the lamp, that the emitter thereof applied to ignite said lamp, capacitor means coupled across said series connected diodes to charge on one alternation of said alternating energy in a direction to back bias said diodes to nonconduction after a predetermined time, and resistive means coupled to discharge said capacitive means when said diodes are rendered nonconductive; and means for coupling said lamp across the series connection of one of said impedances and said electronic switch. 

1. An ignition circuit for igniting a lamp that is energized by a power source comprising in combination: a series-resonant circuit including an inductive impedance and a capacitive impedance; an electronic switch, of the type that automatically disconnects after a predetermined time delay, coupled in series with said resonant circuit and said power source, said switch including a resistor, a capacitor coupled in parallel with said resistor, and a pair of series connected diodes both in the same direction and coupled across said resistor, one of said impedances being coupled to the junction of said diodes; and means for coupling the series connection of said one impedance and said electronic switch across said lamp whereby said lamp is ignited and thereafter said one impedance is disconnected from said lamp by said electronic switch after a predetermined time delay.
 2. The combination in accordance with claim 1 that further includes a second capacitor coupled to said one capacitor with the serial combination of said capacitors being coupled across said resistor.
 3. The combination in accordance with claim 1, wherein said one impedance comprises an inductor.
 4. The combination in accordance with claim 2, wherein said one impedance comprises a capacitor.
 5. An ignition circuit for igniting a lamp that is energized by a power source comprising in combination: a series-resonant circuit including an inductive impedance and a capacitive impedance; an electronic switch of the type that disconnects automatically with a time delay and includes: a bridge connection of four diodes, said bridge having four junctions, a first junction connecting anodes of a first pair of diodes, a second junction connecting cathodes of a second pair of diodes and third and fourth junctions each connecting a cathode of the first pair of diodes to an anode of the second pair of diodes, a resistor, a capacitor connected in parallel with said resistor, said parallel connection being connected across the first and second junctions, the third and fourth junctions being connected to the series-resonant circuit and the power source, so that said switch is in series therewith; and means for coupling the series connection of one of said impedances and said electronic switch across said lamp whereby the lamp is ignited and thereafter the one impedance is disconnected from said lamp by said electronic switch after a predetermined time delay.
 6. The combination in accordance with claim 5, that further includes a further diode connected in series with the capacitor such that the cathode of said diode is connected to said capacitor and the anode thereof to the junction constituted by the anodes of two bridge diodes, and that to the point connecting said capacitor to said further diode there is connected the base of a transistor with the emitter thereof being connected to the anode of said further diode and with the collector thereof being connected to the junction constituted by the cathodes of two bridge diodes.
 7. A circuit for the ignition of two lamps in accordance with claim 3, additionally comprising: a second pair of serially connected diodes both in the same direction and coupled in parallel with and in the same direction as the first pair of diodes; a second series-resonant circuit including an inductive impedance and a capacitive impedance, said inductive impedance connected to said power source and the capacitive impedance connected to the junction connecting the second pair of series connected diodes; and means for connecting a second lamp in parallel with the capacitive impedance of the second series-resonant circuit, the second pair of diodes and the resistor and capacitor of the electronic switch.
 8. An ignition circuit for igniting a lamp that is energized by a power source comprising in combination: a series-resonant circuit including an inductive impedance and a capacitive impedance one of said impedances connected in parallel with said lamp; a pair of diodes connected in series in the same direction, with the common connecting point thereof being connected to the impedance connected in parallel with said lamp, whereas on one hand the cathode of the one diode across a resistor and a transistor connected in parallel therewith, is connected in such a way to said lamp, that the collector thereof is connected to the cathode of the one diode whose emitter is applied to the lamp and whose base, on one hand, via a capacitor is connected to the cathode of the one diode and, on the other hand, via a further diode is applied with its cathode to the base of the transistor, is connected to the lamp whereas, on the other hand, the anode of the other diode, across a further resistor and a further transistor connected in parallel therewith, is connected to the lamp, that the emitter thereof at the anode of said other diode, whose collector is connected to the lamp and whose base is connected on one hand, via a further capacitor, to the lamp and, on the other hand, via a further diode which is applied with its cathode to the base of said further transistor, is connected to the anode of said other diode, whereby said one impedance is disconnected from the lamp after a predetermined time delay.
 9. An ignition circuit for igniting a laMp without a control grid for energization from a source of alternating energy comprising in combination: a series-resonant circuit including a capacitive impedance and an inductive impedance; an electronic switch serially connected to said resonant circuit and said source of alternating energy, said electronic switch including, a pair of series connected diodes coupled to said resonant circuit at their junction so that one of said diodes conducts on one alternation of said alternating energy and the other of said diodes conducts on an opposite alternation of said alternating energy, so that a resonant voltage signal is applied to ignite said lamp, capacitor means coupled across said series connected diodes to charge on one alternation of said alternating energy in a direction to back bias said diodes to nonconduction after a predetermined time, and resistive means coupled to discharge said capacitive means when said diodes are rendered nonconductive; and means for coupling said lamp across the seriEs connection of one of said impedances and said electronic switch. 